The invention relates to a method of detecting displacement of a block of pixels from a first to a second image of a scene.
In one application of such a method, the first and second image are taken from different viewpoints and the displacement reflects parallax of objects in the scene. From U.S. Pat. No. 5,577,130 it is known to measure xe2x80x9cdepthxe2x80x9d from such displacement (depth is the distance between the camera and an object). The depth of an object is inversely proportional to the displacement between the locations where that object is visible in the images from two different viewpoints.
It is desirable that displacement is detected reliably. An important source of unreliability is that one detects displacement of the block to a part of the image that does not depict locations the object concerned, but different locations with similar appearance, or even a different object. Similarly, in case the object is occluded in one of the images, one may detect displacement of an arbitrary different object at the expense of reliability.
U.S. Pat. No. 5,577,130 improves the reliability by starting with a small movement of the viewpoint. As a result it is known that the displacement will be small. This is used to constrain the region in which one has to search for the displaced block. Using the displacement found in this way, the displacement corresponding to larger movements of the viewpoint can be predicted. This in turn is used to constrain the region in which one has to search for the displaced block after a larger movement. Thus, the risk of selecting the wrong displacement is small.
It is a disadvantage of the known method that it imposes constraints on movements of the viewpoint.
It is an object of the invention to provide an opportunity to increase the reliability of the determination of displacements without imposing constraints on the movement of the viewpoint.
The method according to the invention provides for measuring depth by starting with a block from a first image from a first
In an embodiment of the method according to the invention the process is repeated in a number of instances, but with a respective further image taking the place of the second image in each instance. Thus, a depth estimate is obtained for each instance together with a determination of the reliability of this depth estimate. The depth estimates that are considered reliable are composited (for example averaged) to obtain a final depth estimate. In this way a good depth estimate is obtained even if the object is occluded in the second image or some of the further images.